We plan to continue our studies to determine the mechanism by which pretreatment of simian cells with 5' -iododeoxyuridine (IUdR) changes the susceptibility of these cells to infection by the human adenoviruses. It appears that a modification of the pattern of host cell DNA synthesis follows IUdR pre-treatment of simian cells. This modification will be investigated to determine its relationship to the change in cell susceptibility to virus infection. Other studies will continue to characterize cells transformed by viruses photodynamically inactivated following treatment with neutral red and the tumors produced following injection of these cells into hamsters. Although it appears that virus-associated antigens are detected in both types of cells, they are not structural components of the virus. We plan to investigate the nature of these virus associated antigens and their possible role in the maintenance of the transformed state. We will also continue to characterize the temperature-sensitive mutants of measles virus and to determine why some mutants are capable of producing aberrant neural disorders in inoculated animals which are not associated with infection by wild type measles virus.